The Muscular System

Skeletal muscle

A type of muscle that is attached to the skeleton and is under voluntary control.

Smooth muscle

A type of muscle found in the walls of organs, such as the stomach, and is responsible for involuntary movements.

Cardiac muscle

A type of muscle found in the walls of the heart and is responsible for involuntary contractions.

Striation

The visible arrangement of actin and myosin myofilaments in muscle fibers.

Voluntary control

The ability to consciously control the contraction and relaxation of skeletal muscles.

Involuntary

Not under conscious control, such as the contraction of smooth and cardiac muscles.

Fibers

The elongated cells that make up muscle tissue.

Irritability

The ability of a muscle to respond to a stimulus.

Contractibility

The ability of a muscle to shorten in length.

Elasticity

The ability of a muscle to stretch and return to its normal position.

Extensibility

The ability of a muscle to extend in length.

Conductivity

The ability of a muscle to transmit nerve impulses.

Origin

The point where a muscle attaches to the more stationary bone of the axial skeleton.

Insertion

The point where a muscle attaches to the bone that is moved.

Action of Muscles

The main function or movement produced by a muscle.

Direction of the fibers

The orientation or alignment of muscle fibers, such as transversus or rectus.

Location of muscles

The position or placement of a muscle in the body, such as anterior or posterior.

Number of divisions/heads

Some muscles have multiple origins or layers, indicated by prefixes like "bi" or "tri."

Shape of the muscle

The appearance or form of a muscle, such as deltoid or trapezius.

Muscle's points of attachment

The bones or specific spots on bones to which a muscle attaches.

Agonist

The muscle primarily responsible for movement of a body part.

Antagonist

The muscle that counteracts the agonist, lengthening when the agonist contracts.

Concentric contraction

Muscle fibers shorten during contraction.

Isometric contraction

Muscle fibers do not change in length during contraction. (same length)

Isotonic exercise

Controlled shortening and lengthening of the muscle, using dumbbells or barbells.(same tension)

Isometric exercise

Muscles maintain a constant length, often using an immovable surface or object.(same length)

Isokinetic exercise

Involves machines that control the speed of contraction, combining features of isotonic and isometric exercises.

Hypertrophy

Increased size and muscularity of muscles due to increased mitochondrial density, capillary density, and muscle protein levels.

Motor unit recruitment

Increased activation of motor units, resulting in increased strength.

Connective tissue

The tissue that supports and connects muscles, becoming stronger with resistance training.

Sarcomere

The basic structural unit of a muscle fiber, consisting of overlapping thick and thin filaments.

Sarcolemma

The cell membrane of skeletal muscle fibers.

Mitochondrion

An organelle responsible for producing energy in the form of ATP in muscle cells.

Myofibril

A thread-like structure within muscle fibers that contains the contractile proteins actin and myosin.

Dark and Light Bands

Alternating bands within a sarcomere that give skeletal muscle its striated appearance.

Nucleus

The central part of a cell that contains genetic material and controls cellular functions.

Thick Filaments

Bundles of myosin protein within a sarcomere that interact with thin filaments during muscle contraction.

Thin Filaments

Made up of actin protein, these filaments slide past thick filaments during muscle contraction.

Z Disc

A protein structure that anchors the thin filaments and separates one sarcomere from the next.

H Zone

The region within a sarcomere where only thick filaments are present.

A Band

The region within a sarcomere where thick filaments are present, including the H zone and the zone of overlap with thin filaments.

I Band

The region within a sarcomere where only thin filaments are present.

Neuromuscular System

The combination of the nervous system and muscular system that allows for control and movement of skeletal muscles.

Neuromuscular Junction

The point where a motor neuron meets a muscle fiber, allowing for communication between the nervous system and muscular system.

Transverse Tubule (T-Tubule)

Invaginations of the sarcolemma that help stimulate and coordinate muscle contractions.

Sarcoplasmic Reticulum

A membrane network within muscle cells that plays an essential role in controlling and contraction of individual myofibrils.

Z Line

Located at each end of a sarcomere, the point at which the thin filaments attach.

Zone of Overlap

The area within a sarcomere where both thin and thick filaments are present.

Neuromuscular Junction

The point where a motor neuron meets a muscle fiber, allowing for communication between the nervous system and muscular system.

Action Potential

A rapid change in electrical potential across the membrane of a muscle cell, leading to muscle contraction.

Vesicles

Small sacs within the synaptic knob that contain neurotransmitters.

Acetylcholine (ACh)

A neurotransmitter that plays a key role in muscle contraction.

Motor End Plate

The region of the muscle fiber membrane that contains receptors for acetylcholine.

Calcium (Ca2+)

An ion that plays a crucial role in muscle contraction by triggering the release of neurotransmitters and allowing for the interaction between actin and myosin.

Troponin

A protein that binds to calcium ions and regulates the interaction between actin and myosin during muscle contraction.

Tropomyosin

A protein that covers the active sites on actin and prevents interaction with myosin in the absence of calcium.